Magnetic Resonance Imaging (MRI) is a diagnostic device for use in imaging and exploring the internal body without surgery. An MRI has the ability to distinguish healthy and diseased tissue, fat and muscle, and between adjacent structures within the body which other modalities cannot demonstrate.
In operation, a typical MRI apparatus relies upon hydrogen protons which have a dipole movement and therefore behave as would a magnetic compass. The MRI apparatus operates as a large magnet wherein the protons align with the strong magnetic field but are easily disturbed by a brief radio frequency pulse of very low energy so as to alter their alignment. As the protons return to their orientation with the magnetic field, they release energy of a radio frequency that is strongly influenced by the biochemical environment. The released energy is detected and mathematically analyzed for display as a two dimensional proton density image according to the signal intensity of each tissue.
The magnetic coils of a conventional MRI apparatus are permanently fixed within a structure so as to form a large magnet. A patient is placed upon a scanner table that is integrated with the MRI apparatus and slid into the middle of the magnet, namely the bore. A problem with the bore is the extremely small area for placement of the patient and this leads to anxiety. The large and ominous appearance of the scanner together with harsh low monotone sounds which include both soft and loud thumping, produces an eerie and unnatural experience for the patient. Any patient who exhibits claustrophobic tendencies could require sedation before entering the bore. If the patient is above average in size, the problem is exasperated.
It is well known that familiarity of surroundings reduces anxiety. The introduction of familiar images to a person placed within a confining area, such as the MRI bore, will reduce if not eliminate anxiety and certain claustrophobic tendencies of various patients. This reduction can eliminate the need for medicating the patient or the need for a restraining device, all of which may have an adverse effect on a diagnostic test. Thus, a patient who is able to listen to a family member, soft music, or watch a familiar television program will have sufficient distractions so as to avoid concentrating on the immediate surroundings which lead to increased anxiety. In some instances, the diagnostic procedure performed with the MRI is used to evaluate a patient's response to specific visual stimuli. The operator sends a series of images to a screen which is seen by the patient during the MRI procedure and the patient's responses are included in the MRI report. Typically the projector is used with a screen that is located inside the MRI bore near the patient's head.
A problem with introducing conventional audio or video signals into an MRI apparatus is that the MR imager is based upon the use of radio frequencies which will disrupt the audio or video signals. Further, the bore produces a magnetic field which will attract ferro-magnetic metals. Furthermore, the devices that generate the audio and video signals must not interfere with the imaging process. The Applicant has been granted a number of patents which address audio and video signals around an MRI including U.S. Pat. Nos. 5,414,459; 5,892,566; 6,079,829; 6,774,929; and 7,359,026.
The placement of a video projector close to the MRI is the most desirable for operational reasons. However, the magnetic field from the MRI causes problems with the operation of a video projector. The Applicant previously resolved these problems by development of a magnetically inert and RF shielded projector that utilized solid state lighting and an air cooling system. However, the high heat fluxes of modern projectors, coupled with a need for a physically compact MRI-compatible projector, made these designs inadequate, and resulted in inadequate cooling and premature failure of the video projector.
Projector technology is typically based on LCD, LCOS or DLP image generation devices. Each of these devices generates images by modulating some type of light source such as LEDs or filament lamps. A common characteristic of these light sources is that they generate considerable amounts of heat. If this heat is not dissipated, the light source, image generation device or the projector electronics will be adversely affected.
What is needed in the art is a cooling system for this projector technology that operates near an MRI environment.